Alternating copolymerization of carbon monoxide with ethylene or 1-olefins in aqueous emulsion by water-insoluble palladium(II) complexes is reported. Latices of aliphatic polyketones(1-olefin/CO copolymers and ethylene/undec-10-enoic acid/CO terpolymers), prepared by catalytic polymerization, are described for the first time. An in situ catalyst system [{R2P(CH2)3PR2}Pd(OAc)2]/strong acid (R = Ph or (CH2)13CH3) or well-defined complexes [{Ph2P(CH2)3PPh2}PdMe(NCCH3)]+Y-(Y- = [B{3,5-(F3C)2C6H3}4]- or SbF6-) were used in the form of a solution of the palladium(II) complex in miniemulsion droplets of a hydrocarbon dispersed in the continuous aqueous phase. Catalyst activities of up to 5 X 103 TO h-1 slightly exceed those of nonaqueous polymerizations in methanol with the same catalysts. Polymer molecular weights (GPC vs PMMA standards) are typically Mw 2 X 105 (ethylene copolymers) respectively Mw 2 X 104 (1-olefin copolymers) with Mw/Mn 2-4. The 1-olefin copolymers exhibit glass transition temperatures of Tg = +10 to -55°C, which is in the range desirable for latex applications.